Electrochromic element, materials for use in such element, processes for making such element and such materials and use of such element in an electrochromic glass device

ABSTRACT

An electrochromic element useful in an electrochromic glass or mirror device and a process for making such element. The element is a five-layered structure including an electrolyte ion conducting layer interposed between first and second inorganic electrochromic layers which are interposed between a pair of conductive electrodes. The second inorganic electrochromic layer is amorphous. The first and second inorganic electrochromic layers are different and are capable of exhibiting color-forming properties complementary to one another upon the incorporation of at least one H, Li, Na, K, Ag, Cu or Tl ion. The electrolyte ion conducting layer may be a copolymer of ethylene oxide, butylene oxide or methyl glycidyl ether, and optionally a small amount of allyl glycidyl ether, along with an ionizable salt, or may be a polyurethane gel formed by reacting the copolymer with triisocyanate, along with an ionizable salt. The second inorganic electrochromic layer comprises a transition element chalconide or halide which exhibits a color change when shifting between the +2 and +3 valence states or between the +3 and +4 valence states. The second inorganic electrochromic layer may be produced by an electrochemical process, a chemical process, a physical process or by a solid state process. The electrochromic element may also comprise a plurality of five-layer structures in tandem, each pair separated by a substrate. The electrochromic element of the invention is also useful as a supercapacitor.

This application is a continuation-in-part of application Ser. No.07/379,225, filed Jul. 13, 1989, now U.S. Pat. No. 5,086,351.

BACKGROUND OF THE INVENTION

The present invention relates to electrochromic elements, and moreparticularly to laminated electrochromic glass devices and processes formaking such devices.

Electrochromic materials generally are materials which change color uponapplication of electrical current to induce an electrochemical reactionin the material.

Electrochromic devices are known which comprise a laminated structureincluding an electrolyte ion conducting layer sandwiched between anelectrochromic layer and a counter electrode layer, all sandwichedbetween a pair of conductive electrodes composed of, for example,indium-tin oxide.

Many of the prior art electrochromic elements utilize WO₃ as theelectrochromic color-forming layer. It is known that WO₃ changes from aclear, transparent state to a colored state upon undergoing thereaction: ##STR1## wherein Z is selected from H or alkali metals such asLi or Na.

It is also known from the nonaqueous secondary battery art that variousother metals will display electrochromic properties when changing fromone valence state to another. Specifically, it is known that sometransition metals exhibit electrochromic properties when moving betweenthe +2 and +3 valence states and other transition metals exhibit suchproperties when changing between the +3 and +4 valence states.

Heretofore, the art has had difficulty utilizing the electrochromicproperties of WO₃ in combination with the electrochromic properties ofthese other known transition metal oxides. For example, it is disclosedby U.S. Pat. No. 4,750,816 that "oxidatively color-forming materialssuitable as opposing electrodes of reductive color-forming layerscomprising WO₃, etc. are not found in inorganic materials." (Column 1,lines 42-45). This is due to several factors, such as the difficulty indiscovering oxidative color-forming materials which (1) have a highenough ion exchange capacity; (2) exhibit an adequate transparency or,even better, exhibit color changes complementary to those of WO₃ ; and(3) have a range of working potential compatible with that of the othermaterials in the electrochromic element.

The term "complementary" color changes, as used herein, means exhibitingopposite color-forming tendencies upon the insertion of an ion. WO₃colors when an ion is inserted therein and thus materials"complementary" to WO₃ would bleach upon ion insertion. Thus, anelectrochromic element utilizing a layer of WO₃ along with a layer of amaterial having a complementary color change to WO₃ would have twobleached electrochromic layers when an ion was inserted into thecomplementary layer and two colored layers when an ion was inserted intothe WO₃ layer. This would enable an additive color effect to beattained.

Because of the aforementioned difficulties, prior art electrochromicdevices tended to utilize either a single electrochromic layer of WO₃ orother electrochromic material to produce the desired electrochromiccolor change effect, or utilized either an inorganic compound whichundergoes little or no color change upon ion insertion and removal or anorganic compound as the opposing or counter electrode to the WO₃ layer.The use of a single electrochromic layer of WO₃ or a layer of WO₃ inconjunction with a counter electrode which remains transparent upon ioninsertion and removal, suffers from the disadvantage that the differencein the amount of light that is transmitted through the layer in theclear and colored states is limited by the extent of color change of theWO₃ material. In addition, electrochromic devices utilizing an organicelectrochromic layer suffer from the disadvantage that these layers areunstable over long periods of time and thus their long termcolor-forming durability is questionable.

It is an object of the present invention to provide a novelelectrochromic element.

It is another object of the present invention to provide a novelelectrochromic glass device.

It is another object of the present invention to provide anelectrochromic element which is characterized by having a largedifference between the percentage of visible light transmitted by theelement in the colored state and the percentage of visible lighttransmitted by the element in the bleached state.

It is another object of the present invention to provide anelectrochromic element which is characterized by having a largedifference between the percentage of radiant heat transmitted by theelement in the colored state and the percentage of radiant heattransmitted by the element in the bleached state.

It is another object of the present invention to provide anelectrochromic element whose color-forming properties exhibit excellentlong term durability.

It is another object of the present invention to provide anelectrochromic element characterized by having an excellent responsetime, i.e., the period of time to change between the bleached state andthe colored state is low.

It is another object of the invention to provide an electrochromicelement that can operate effectively over a wide range of temperatures.

It is a further object of the invention to provide an electrochromicelement that does not utilize toxic or corrosive materials.

It is another object of the invention to provide an element that canoperate effectively as a supercapacitor.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention.

SUMMARY OF THE INVENTION

As embodied and broadly described herein, the electrochromic element ofthe present invention can be a five-layered structure which comprises apair of electrodes at least one of which is transparent, first andsecond inorganic electrochromic layers interposed between the pair ofelectrodes and an ion conducting layer of an electrolyte interposedbetween the first and second inorganic electrochromic layers. The secondinorganic electrochromic layer is amorphous. The first and secondinorganic electrochromic layers are preferably composed of differentmaterials each of which is capable of exhibiting electrochromicproperties upon the incorporation of at least one ion of an elementselected from the group consisting of H, Li, Na, K, Ag, Cu and Tl. Inaddition, the electrochromic properties of the first and secondinorganic electrochromic layers are preferably complementary to oneanother.

The electrochromic element of the invention, as embodied and broadlydescribed herein, more particularly has a first inorganic electrochromiclayer which is preferably WO₃ and a second inorganic electrochromiclayer which is amorphous, preferably comprising a fourth periodtransition element chalconide or halide which exhibits a color changewhen shifting between the +2 and +3 or between the +3 and +4 valencestates. The fourth period transition metal can be Ni, Co, Mn, Cr, V, Tior Fe. The chalconide or halide can be O, S, F or Cl.

In another aspect of the invention, as embodied and broadly describedherein, an amorphous electrochromic material is provided which may beutilized as the second inorganic electrochromic layer in theelectrochromic element of the invention. This material comprises atransition element chalconide or halide which exhibits a color changewhen shifting between the +2 and +3 valence states or between the +3 and+4 valence states and can be represented by the formula M_(x) T^(n) _(y)T^(n+m).sub.(uz-ny-x)/(n+m) X^(u) _(z). M is at least one elementselected from H, Li, Na, K, Ag, Cu and Tl. T is a transition element ofthe fourth period of the periodic table having an oxidation numberranging from 2 to 4. T can be Ni, Co, Mn, Cr, V, Ti or Fe. X is at leastone element selected from O, S, F and Cl. n, n+m and u are oxidationnumbers. x is the moles of M⁺ ions that are incorporated into theelectrochromic material, y is the moles of T at the oxidation number nand z is the moles of X. x, y, z, u≧0, 2≦n≦3, 1≦m≦2, n+m≦4.

The electrochromic element of the invention utilizing the aboveamorphous electrochromic material as the second inorganic electrochromiclayer is capable of exhibiting a first color state wherein the firstinorganic electrochromic layer is bleached and has the composition WO₃and the second inorganic electrochromic layer is bleached and has thecomposition M_(x) T_(y) ^(n) X_(z) ^(u), and a second color statewherein the first inorganic electrochromic layer is colored and has thecomposition M.sub.Δx WO₃ and the second inorganic electrochromic layeris colored and has the composition M_(x-)Δx T^(n) _(y-)Δx/mT^(n+m).sub.Δx/m X^(u) _(z). The first color state has a maximumtransmissivity and the second color state has a less than maximumtransmissivity. The formula M_(x) T_(y) ^(n) T^(n+m).sub.(uz-ny-x)/(n+m)X^(u) _(z) represents intermediate insertion states.

In another aspect of the invention, as embodied and broadly describedherein, an electrochromic element is provided which comprises aplurality of five-layered electrochromic elements as described above,positioned in juxtaposed surface to surface relation with one another,each pair of five-layered elements separated by a substrate layer. Morespecifically, a device comprising a pair of five-layered elementscomprises the following layers, in order: a first transparent substrate;a first transparent conductive electrode; a first inorganicelectrochromic layer; a first ion conducting layer of an electrolyte; afirst amorphous inorganic electrochromic counter electrode layer; asecond transparent conductive electrode; a second transparent substrate;a third transparent conductive electrode; a second amorphous inorganicelectrochromic counter electrode layer; a second ion conducting layer ofan electrolyte; a second inorganic electrochromic layer; a fourthconductive electrode which may be transparent or reflective; and a thirdtransparent substrate. The first and second inorganic electrochromiclayers are preferably different from the first and second amorphousinorganic electrochromic counter electrode layers. The first and secondinorganic electrochromic layers and the first and second amorphouselectrochromic counter electrode layers are preferably capable ofexhibiting electrochromic properties upon the incorporation of an ion ofan element selected from H, Li, Na, K, Ag, Cu and Tl. In addition, theelectrochromic properties of the first and second inorganicelectrochromic layers preferably are complementary to the electrochromicproperties of the first and second amorphous inorganic electrochromiccounter electrode layers.

The invention also relates to processes for making the amorphouselectrochromic materials described above. As embodied and broadlydescribed herein, one such process for producing an amorphouselectrochromic material comprises:

A first step of forming an original thin film consisting essentially ofTO, T(OH)₂ and TOOH by sputtering a target comprising T with O₂ /H₂plasma;

a second step of electrochemically processing the original thin film inalkali metal hydroxide solution to give a layer consisting essentiallyof TO and TOOH;

a third step of electrochemically processing the layer consistingessentially of TO and TOOH in a liquid electrolyte comprising anionizable salt MZ and a polar solvent of this salt, wherein M is anelement selected from H, Li, Na, K, Ag, Cu and Tl and Z is a strong acidanion selected from ClO₄ ⁻, CF₃ SO₃ ⁻ and N(CF₃ SO₂)₂ ⁻, to incorporatexM⁺ ions into the layer to form an amorphous electrochromic materialhaving the composition M_(x) T^(n) _(y) T^(n+m).sub.(2z-ny-x)/(n+m)O_(z) ;

wherein T is a transition element of the fourth period of the periodictable having an oxidation number ranging from 2 to 4 and is selectedfrom Ni, Co, Mn, Cr, V, Ti and Fe; M is at least one Group 1A, 1B or 3Belement selected from H, Li, Na, K, Ag, Cu and Tl; n and n+m representoxidation numbers and x, y and z represent the moles of M, moles of T atoxidation number n and moles of O, respectively.

Another process for producing an amorphous electrochromic material, asembodied and broadly described herein, comprises:

a first step of sputtering a target of M.sub.α T₁₋α O, wherein 0≦α≦1.0,to form a thin film which comprises M,T^(n),T^(n+m) and O;

a second step of electrochemically processing the thin film in a liquidelectrolyte comprising an ionizable salt MZ and a polar solvent of thissalt, wherein M is an element selected from H, Li, Na, K, Ag, Cu and Tland Z is a strong acid anion selected from C1O₄ ⁻, CF₃ SO₃ ⁻ and N(CF₃SO₂)₂ ⁻, to incorporate M⁺ ions in the thin film to form an amorphouselectrochromic material having the composition M_(x) T^(n) _(y)T^(n+m).sub.(2z-ny-x)/n+m) O_(z) ;

wherein T is a transition element of the fourth period of the periodictable having an oxidation number ranging from 2 to 4 and is selectedfrom Ni, Co, Mn, Cr, Ti and Fe; M is at least one element selected fromH, Li, Na, K, Ag, Cu and Tl; and n and n+m represent oxidation numbers;and x, y, and z represent mole fractions.

The invention also relates to a method of forming an amorphous inorganicelectrochromic material. This method comprises:

sputtering a layer of a conductive electrode material on a firstsubstrate;

sputtering a layer of an amorphous inorganic electrochromic materialonto said conductive electrode layer on said first substrate;

depositing a solid polymer electrolyte onto said amorphous inorganicelectrochromic layer;

assembling a lithium electrode on a second substrate into juxtaposedcontact with said solid polymer electrolyte;

applying a first voltage differential between said conductive electrodematerial and said lithium electrode to incorporate lithium ions intosaid amorphous inorganic electrochromic layer;

applying a second voltage differential between said conductive electrodematerial and said lithium electrode to remove lithium ions from saidamorphous inorganic electrochromic layer; and

removing said lithium electrode on said second substrate and said solidpolymer electrolyte from said amorphous inorganic electrochromic layer.

The invention also relates to a method of manufacturing theelectrochromic device as described above. This method, as embodied andbroadly described herein, preferably comprises:

sputtering a layer of a conductive electrode material on a firstsubstrate;

sputtering a layer of an inorganic electrochromic material onto theconductive electrode layer on the first substrate;

sputtering a layer of a conductive electrode material on a secondsubstrate;

sputtering a layer of an amorphous inorganic electrochromic materialonto the conductive electrode layer on the second substrate; and

assembling an ion conducting layer of an electrolyte between thesputtered sides of the first and second substrates.

The invention further relates to a method of manufacturing theelectrochromic device comprising a pair of five-layered electrochromicelements in back to back relation. Such a method, as embodied andbroadly described herein, comprises:

sputtering a first layer of a conductive electrode material on a firstsubstrate;

sputtering a first layer of an inorganic electrochromic material ontothe first conductive electrode layer on the first substrate;

sputtering a second layer of a conductive electrode material on a secondsubstrate;

sputtering a second layer of an inorganic electrochromic material ontothe second conductive electrode layer on the second substrate;

sputtering a third layer of a conductive electrode material on one sideof a third substrate and a fourth layer of a conductive electrodematerial on the other side of the third substrate; and

sputtering a layer of an amorphous inorganic electrochromic material onthe third and fourth conductive electrode layers on each side of thethird substrate. The sputtered side of the first substrate is assembledinto juxtaposed contact with one side of the third substrate with an ionconducting layer of an electrolyte interposed therebetween. Thesputtered side of the second substrate is then assembled into juxtaposedcontact with the other side of the third substrate with an ionconducting layer of an electrolyte interposed therebetween.

The present invention also provides a supercapacitor comprising a pairof conductive substrates, first and second inorganic electrochromiclayers interposed between the pair of conductive substrates and an ionconducting layer of an electrolyte interposed between the first andsecond inorganic electrochromic layers.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate preferred embodiments of theinvention and together with the detailed description of the preferredembodiments herein, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a construction of one embodiment ofthe laminate electrochromic device of the present invention.

FIG. 2 is a sectional view showing a construction of a second embodimentof the laminate electrochromic device of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

In accordance with the present invention, there is provided anelectrochromic element comprising a pair of electrodes at least one ofwhich is transparent, first and second inorganic electrochromic layersinterposed between the pair of conductive electrodes and an ionconducting layer of an electrolyte interposed between the first andsecond inorganic electrochromic layers. The second inorganicelectrochromic layer is amorphous. As used herein, the term amorphousmeans amorphous to X-rays. The first inorganic electrochromic layer canbe amorphous or crystalline. The first and second inorganicelectrochromic layers are different and are capable of exhibitingelectrochromic properties upon the incorporation of an ion of an elementselected from H, Li, Na, K, Ag, Cu and Tl. The electrochromic propertiesof the first and second inorganic electrochromic layers arecomplementary. As embodied in FIG. 1, electrochromic element 10comprises a pair of conductive electrodes 12 and 14. Conductiveelectrodes 12 and 14 may both be transparent or one may be transparentand the other reflective.

In a preferred embodiment of the invention, electrochromic element 10 isutilized in an electrochromic glass device. In such an embodiment,conductive electrodes 12 and 14 are both transparent and are formed ontwo substrates 22 and 24 made of, for example, glass or plastic.Conductive electrodes 12 and 14 may be any of those materials known inthe art to be useful as transparent conductive electrodes and arepreferably composed of indium tin oxide, which is a composition of In₂O₃ containing 5 wt. % of SnO₂, or fluorine doped tin oxide (SnO₂ :F).When utilizing indium tin oxide as conductive electrodes 12 and 14, theindium tin oxide is preferably deposited on float glass. Pyrrolyticglass (SnO₂ :F) as supplied by the glass industry may also be utilized,which would function as both conductive electrodes 12 and 14 andsubstrates 22 and 24.

In another embodiment of the invention, electrochromic element 10 isutilized in a mirror. In such an embodiment, one of conductiveelectrodes 12 and 14 is reflective and the other is transparent. Theconductive electrode 12 or 14 that is reflective may be any of thosematerials known in the art to be useful as reflective conductiveelectrodes, such as Al, Au or Ag.

In accordance with the present invention as embodied in FIG. 1, firstinorganic electrochromic layer 16 and second inorganic electrochromiclayer 18 are interposed between conductive electrodes 12 and 14. Firstinorganic electrochromic layer 16 preferably comprises WO₃. WO₃ isbleached in its normal state and is thus transparent. However, thecompound WO₃ has the property that it exhibits a colored state when ionssuch as Li⁺ are incorporated therein. First inorganic electrochromiclayer 16 may alternatively comprise TiO₂ or MoO₃, or any of thosecompounds known in the art that are bleached in the normal state andcolored when ions such as H⁺, Li⁺, Na⁺, K⁺, Ag⁺, Cu⁺, and Tl⁺ areincorporated therein.

In accordance with the invention, first inorganic electrochromic layer16 may be produced by sputtering a tungsten target to form a film of WO₃or alternatively, the film of WO₃ may be electrochemically processed.

In accordance with the invention, second inorganic electrochromic layer18 preferably comprises a fourth period transition element chalconide orhalide having the property of exhibiting a color change when shiftingbetween the +2 to +3, or between the +3 and +4 valence states. Thecomposition of second inorganic electrochromic layer 18 can berepresented by the formula M_(x) T^(n) _(y) T^(n+m).sub.(uz-ny-x)/(n+m)X^(u) _(z). T is a transition element of the fourth period of theperiodic table which can be Ni, Co, Mn, Cr, V, Ti or Fe, and M is atleast one element selected from H, Li, Na, K, Ag, Cu and Tl. X can be O,S, F or Cl. n, n+m and u represent oxidation numbers. x represents themoles of M⁺ ions that are incorporated into second inorganicelectrochromic layer 18. y represents the moles of T at the oxidationnumber n and z is the moles of x. x, y, z, u≧0, 2≦n≦3, 1≦m≦2, n+m≦4.

In accordance with the invention, Li, Na, K, Ag, Cu or Tl ions can beincorporated into first and second inorganic electrochromic layers 16and 18 without any incorporation of H⁺ ions. However, during assembly ofelectrochromic element 10, it is possible that some amount of water mayenter the system. The presence of water in the electrochromic system maycause certain amounts of H⁺ ions to be formed which will inevitablybecome incorporated into first and second inorganic electrochromiclayers 16 and 18 along with Li⁺, Na⁺, K⁺, Ag⁺, Cu⁺ or Tl⁺ ions. Thepresence of H⁺ ions in the system can cause problems in that WO₃degrades in the presence of H₂ O, which may be formed as a by-product.In addition, H₂ gas may be formed as a by-product from H⁺ ions and cancause bubble formation (often called "outgassing"). On the other hand,H⁺ ions are smaller than Li⁺, Na⁺ , K⁺, Ag⁺, Cu⁺ or Tl⁺ ions and thusare more mobile which results in faster incorporation and extractionfrom first and second inorganic electrochromic layers 16 and 18. Amixture of Li, Na, K, Ag, Cu or Tl and hydrogen ions incorporated intofirst and second inorganic electrochromic layers 16 and 18 will havesome of the characteristics of both H⁺ incorporation and non-hydrogen M⁺incorporation.

In accordance with the invention, second inorganic electrochromic layer18 may be produced by an electrochemical method of first sputtering atarget comprised of a transition metal T with a plasma of O₂ /H₂ to forman original thin film layer consisting essentially of a mixture of TO,T(OH)₂ and TOOH. This original layer is then preferablyelectrochemically processed in an alkali metal hydroxide solution, forinstance NaOH, 1N solution, wherein the original layer is the cathodeand the anode is a platinum electrode. This electrochemical step yieldsa layer consisting essentially of TO and TOOH. The resulting layer isthen electrochemically processed in a liquid electrolyte solution withone electrode consisting of the TO/TOOH mixture with an opposing lithiumelectrode. The liquid electrolyte may comprise an ionizable salt MZ anda polar solvent of this salt, such as propylene carbonate and (C₂ H₅)₂NSO₂ N(C₂ H₅)₂, wherein M is as defined earlier herein and Z is a strongacid anion selected from ClO₄ ⁻, CF₃ SO₃ ⁻ and N(CF₃ SO₂)₂.sup. -. Theelectrochemical reaction that takes place causes a particular molefraction of M⁺ ions, designated herein as x, to become incorporated intothe layer in a first stage. This electrochemical reaction is designatedby the following equation:

    [(1-2x)TO,2xTOOH]+xM.sup.+ +xe.sup.- →[(1-2x)TO,xMTO.sub.2,xHTOOH]

While not intending to be bound by any theory of how the inventionworks, applicants believe that the H atoms in TOOH are loosely attachedand may migrate into the interior of the layer. It is believed that, ina first stage, some amount of M⁺ ions are immediately incorporated intothe electrochromic layer and a solid solution is spontaneously formedwhich comprises M,T^(n),T^(n+m) and O. This first stage incorporation ofM⁺ ions is partially irreversible.

In addition to the M⁺ ions that can be incorporated into theelectrochromic layer in a first stage, an additional amount of M⁺ ionscan be incorporated into the electrochromic layer in a second stage.This second stage incorporation is reversible, which enables the ions tobe inserted and removed from the layer.

The present invention utilizes the property of transition elements suchas Ni, Co, Mn, V and Fe that undergo a color change when moving betweenthe +2 and +3 valence states and the property of transition elementssuch as Fe, Ti and Cr that undergo a color change when moving betweenthe +3 and +4 valence states. Generally, Ni, Co, Mn, and V are coloredin the +3 valence state and bleached (less colored in the case of Co) inthe +2 valence state. Cr and Fe are generally bleached in the +3 stateand colored in the +4 state. Ti generally exhibits only a small colorchange when moving between the +3 and +4 valence states and thus Tibased compounds could also be utilized as first inorganic electrochromiclayer 16.

In accordance with the invention, an alternative method for producingsecond inorganic electrochromic layer 18 is a physical preparation whichcomprises a first step of sputtering a target of M.sub.α T₁₋α O, whereinO<α≦1.0 and w represent mole fraction, to form a thin film whichcomprises M, T^(n), T^(n+m) and O; and a second step ofelectrochemically processing the thin film in a liquid electrolytecomprising a polar solvent selected from propylene carbonate and (C₂H₅)₂ NSO₂ N(C₂ H₅)₂ and an ionizable salt MZ, wherein M is an elementselected from H, Li, Na, K, Ag, Cu and Tl and Z is a strong acid anionselected from ClO₄ ⁻, CF₃ SO₃ ⁻ and N(CF₃ SO₂)₂ ⁻, to incorporate xM⁺ions into the thin film to form the electrochromic material having thecomposition M_(x) T^(n) _(y) T^(n+m).sub.(2z-ny-x)/(n+m) O_(z).

In accordance with the invention, an alternative method for producingeither first or second inorganic electrochromic layers 16 or 18 is amethod that consists of chemically inserting atoms such as lithium orsilver atoms into either layer. This chemical insertion can be achievedby using alkali metal active organic solutions similar to those utilizedto intercalate Li⁺ ions in various host structures. (See French PatentNo. 2,569,058). This method overcomes the potential problem of H⁺contamination since protons are incapable of co-existing with Li, Na, K,Ag, Cu or Tl in these solutions.

In accordance with the invention, an amorphous inorganic electrochromicmaterial can be produced by inserting and extracting lithium ions priorto assembling the device without the use of any liquid electrolyte. This"solid state" process enables an amount of ions to be inserted inaddition to the amount inserted into the deposited films. It has beenfound that this process provides the following advantages: improvedreversibility of ion exchange; avoidance of liquid electrolyte diffusioninto the other layers of the device; and capability of cycling thedevice at elevated temperatures which reduces the processing time andstabilizes the layers.

In accordance with the invention, the "solid state" process for formingthe electrochromic layer comprises forming an "electrochromic layerlaminate" which consists of: substrate/transparent conductiveelectrode/electrochromic layer/solid polymer electrolyte (SPE). Thesolid polymer electrolyte may be crosslinked and should be a materialthat is conductive to Li⁺. A lithium electrode on a substrate is thenplaced into juxtaposition with the electrochromic layer laminate. Thiscan be accomplished by: (1) applying a lithium foil to the electrolytelayer of the electrochromic layer laminate; (2) forming a solid polymerelectrolyte/lithium/substrate laminate ("lithium laminate") andcontacting the SPE of the electrochromic layer laminate with the SPE ofthe lithium laminate under pressure in a vacuum; or (3) forming alithium laminate and adhering the SPE of the lithium laminate with theSPE of the electrochromic layer laminate with a small amount ofadditional SPE acting as a crosslinkable adhesive.

The resulting device, which consists of substrate/transparent conductiveelectrode/electrochromic layer/SPE/lithium/substrate, is then "cycled"by application of a voltage differential to first insert and then removeLi⁺ from the electrochromic layer. The SPE/lithium electrode/substratecan then be removed by, for example, peeling away. The remainingsubstrate/conductive electrode/electrochromic layer can then beassembled in a final electrochromic device.

It has been discovered by the present inventors that, although it may beadvantageous in many cases to insert and remove ions from the inorganicelectrochromic material prior to assembling the electrochromic device,it may not always be necessary to do so. Thus, it may be advantageous insome cases to assemble the electrochromic device of the inventionwithout any electrochemical processing of the inorganic electrochromiclayers.

In accordance with the invention, second inorganic electrochromic layer18 is amorphous rather than crystalline or polycrystalline. Somecrystalline materials are capable of reversibly intercalating M⁺ ions.These materials are believed to have a long range tunnel-like orleaflet-like crystal order, at least along one direction. However, suchstructures are very difficult to obtain in thin films by knowntechniques. Presently available techniques for producing thin filmsyield, at best, polycrystalline structures, i.e., materials havingcrystalline domains that are randomly connected. Polycrystallinestructures have intercalation properties (exchange capacity andkinetics) that are significantly inferior to those of monocrystals. Thisis believed to be due to the fact that the crystallites are randomlyoriented and thus there is no continuity of tunnels from one grain tothe other. As a result, potential barriers to ion migration exist at theboundaries between crystallites.

The process of the present invention, on the other hand, can producethin films that are amorphous and thus are capable of very high exchangecapacities and superior kinetics, as compared to polycrystallinematerials. Performance of the amorphous thin films of the presentinvention actually approaches that of monocrystals.

In accordance with the present invention as embodied in FIG. 1, ionconducting layer 20 is interposed between first and second inorganicelectrochromic layers 16 and 18. Ion conducting layer 20 preferablyconsists of a solid polymeric electrolyte, which is an amorphous solidsolution comprising a copolymer of ethylene oxide and methyl glycidylether and at least one ionizable salt. Alternatively, the copolymer maybe ethylene oxide and butylene oxide. The preferred proportions of thecopolymer are 75% ethylene oxide and 25% methyl glycidyl ether orbutylene oxide. In addition, a small amount of allyl glycidyl ether (5%)may be included in the copolymer. The molecular weight of the copolymerpreferably ranges between 30,000 and 2,000,000. The ionizable saltutilized in conjunction with the solid copolymer, can be a mixture ofMClO₄ and MN(CF₃ SO₂)₂ or can consist entirely of MN(CF₃ SO₂)₂, whereinM is selected from H, Li, Na, K, Ag, Cu or Tl, and is preferably Li. Thesolid polymeric electrolyte may also include a plasticizer such as (C₂H₅)₂ NSO₂ N(C₂ H₅)₂. (See French Patent No. 2,606,216).

In accordance with an alternative embodiment of the invention, ionconducting layer 20 may comprise a polyurethane made by reactingtriisocyanates with the above-mentioned copolymers having a lowmolecular weight (1,000-20,000) along with at least one of theabove-mentioned ionizable salts. Such a polyurethane network utilized inion conducting layer 20 chemically crosslinks and hardens attemperatures near room temperature. The basic chemical reaction is:##STR2## These polyurethane networks have the advantage of nearlyperfect optical transparency.

In accordance with the invention, the ion conducting layer 20 may alsoutilize a liquid electrolyte such as LiClO₄ -propylene carbonate.However, a solid polymeric electrolyte for use in ion conducting layer20 is preferable over liquid electrolytes because the solid polymers aremuch easier to handle in assembling the electrochromic device andpresent far fewer safety concerns in the assembled device from potentialleaking. One important factor which can cause "haze" problems inelectrochromic elements is the crystallization of the ion conductinglayer. The solid polymeric electrolyte of the invention comprising acopolymer of ethylene oxide and methyl glycidyl ether or butylene oxidealong with at least one ionizable salt and the solid polymericelectrolyte comprising a polyurethane gel and at least one ionizablesalt each provides an efficient layer for conducting ions between firstand second inorganic electrochromic layers 16 and 18 without significantcrystallization of the solid polymer electrolyte, i.e., the solidpolymer electrolyte remains amorphous. In addition, the copolymerincluding butylene oxide has the advantage of being less hydrophilic.

The ion conducting macromolecular material of the present invention canbroadly be any polymer-based material exhibiting an ionic conductivityat least equal to 10⁻⁷ siemens/cm at room temperature and an electronicconductivity lower than 10⁻¹⁰ siemens/cm.

In particular, the ion conducting macromolecular material can comprise asolid solution of at least one ionizable salt, especially a Group 1A, 1Bor 3B element salt and more particularly a lithium salt, in a plasticpolymeric material comprising at least in part one or more polymersand/or copolymers of monomers containing at least one heteroatom,especially oxygen or nitrogen, able to form donor/acceptor bonds withthe cation of the ionizable salt, the polymers being in particular,chosen among polyethers, and more especially among the polymers ofethylene oxide or propylene oxide (see European Patent Application No.0013199). The plastic polymeric material can comprise at least onecopolymer of ethylene oxide and of another cyclic oxide, said copolymerhaving either the structure of a statistical copolymer (U.S. Pat. No.4,578,326) which may be crosslinked (French Patent No. 2,570,224) or theform of a polyurethane network resulting from the reaction of asequenced copolymer of ethylene oxide and another cyclic oxide with acoupling agent consisting of an organic polyisocyanate (French PatentNo. 2,485,274). Moreover, the ionizable salts mentioned in EuropeanPatent Application No. 0013199 can be replaced in whole or in part byionizable salts such as alkali metal closoboranes (French Patent No.2,523,770), alkali metal tetrakis-trialkylsiloxyalanates (French PatentNo. 2,527,611), alkali metal bis(perhalogenoalkylsulfonyl)imides orbis(perhalogenoacyl)imidides (French Patent No. 2,527,602), alkali metaltetraalkynylborates or aluminates (French Patent No. 2,527,610), alkalimetal derivatives of perhalogenoalkylsulfonylmethane orperhalogenoacetylmethane (French Patent No. 2,606,218), or alkali metalsalts of polyethoxylated anions (European Patent Application No.0,213,985).

The ion conducting macromolecular material of the invention can alsobroadly consist of a solid solution of an ionizable salt, for exampleone of those mentioned above, in a polymeric material made up with anorganometallic polymer in which at least two polyether chains are linkedby a metallic atom selected from Al, Zn and Mg (French Patent No.2,557,735) or among Si, Cd, B and Ti (French Patent No. 2,565,413), orin a polymeric material consisting of a polyphosphazene bearing on eachphosphorus atom two polyether groups such as polyethylene oxide groups.The ion conducting macromolecular material may also be selected from themixtures of polymers having a solvating and/or polar character with anysalt, acid or base sufficiently dissociated in the polymer to obtain theappropriate conductivity, from polymers bearing ionizable functionsresulting in anions or cations attached to the macromolecular chains,from protonic conductors such as those described in French Patent No.2,593,328 or mixtures of inert polymers with mineral or organic ionconducting materials dispersed in the polymer matrix.

In a preferred embodiment of the present invention, electrochromicelement 10 is interposed between a pair of glass or plastic substrates22 and 24. Such an arrangement forms an electrochromic device. Theelectrochromic device can be manufactured by sputtering on a glass orplastic substrate 22 or 24, conductive electrode 12 which may becomposed of indium-tin oxide or fluorine doped tin oxide (SnO₂ :F).First inorganic electrochromic layer 16 is then sputtered ontoconductive electrode 12. On a second glass or plastic substrate 22 or24, conductive electrode 14 is sputtered, and second inorganicelectrochromic layer 18 is sputtered onto conductive electrode 14. Thetwo sputtered glass substrates are then assembled with ion conductinglayer 20, which may be a solid polymeric electrolyte, interposedtherebetween.

In accordance with the invention, it should also be possible tomanufacture electrochromic element 10 by depositing all of the activelayers, i.e., conductive electrodes 12 and 14, first and secondinorganic electrochromic layers 16 and 18 and ion conducting layer 20 inthe form of a gel. (See Solid State Ionics 28-30 (1988)-1722).

In accordance with the invention, M⁺ ions can be incorporated into firstinorganic electrochromic layer 16 prior to being assembled in theelectrochromic element 10. Alternatively, M⁺ ions can be incorporatedinto second inorganic electrochromic layer 18 prior to assembly into theelectrochromic device. In either case, the application of a voltagedifferential between conductive electrodes 12 and 14 will cause the M⁺ion to move out of one inorganic electrochromic layer 16 or 18, throughion conducting layer 20 and into the other inorganic electrochromiclayer 16 or 18, thereby causing each of first and second inorganicelectrochromic layers 16 and 18 to become either bleached or colored.

In accordance with the invention, the voltage differential betweenconductive electrodes 12 and 14 sufficient to cause M⁺ ions to beincorporated into either first or second inorganic electrochromic layers16 and 18 is less than or equal to 3.5 volts vs. Li. This makes firstand second inorganic electrochromic layers 16 and 18 compatible with ionconducting layer 20 when utilizing a solid polymeric electrolytecontaining a lithium salt which will decompose at potentials greaterthan or equal to 3.5 volts vs. Li.

In an alternative embodiment of the invention, as embodied in FIG. 2,electrochromic element 28 comprises:

a first transparent conductive electrode 30 which may be indium tinoxide or fluorine doped tin oxide;

first inorganic electrochromic layer 32 which may be WO₃, MoO₃ or TiO₂ ;

first ion conducting layer of an electrolyte 34 which may be a solidpolymeric electrolyte comprising a terpolymer of ethylene oxide,butylene oxide and allyl glycidyl ether and at least one ionizable saltor may be a solid polymeric electrolyte comprising a polyurethane geland at least one ionizable salt;

first amorphous inorganic electrochromic counter-electrode layer 36which may be the same transition element compounds as disclosed earlierfor second inorganic electrochromic layer 18 of FIG. 1;

second transparent conductive electrode 38 which may be indium tin oxideor fluorine doped tin oxide;

transparent substrate 40 which may be glass or a plastic;

third transparent conductive electrode 42 which may be indium tin oxideor fluorine doped tin oxide;

second amorphous inorganic electrochromic counter-electrode layer 44which may be the same transition element compounds as disclosed earlierfor second inorganic electrochromic layer 18 of FIG. 1;

second ion conducting layer of an electrolyte 46 which may be the samematerials as for layer 34;

second inorganic electrochromic layer 48 which may be WO₃, MoO₃ or TiO₂;

and fourth conductive electrode 50 which may be transparent orreflective.

First and second inorganic electrochromic layers 32 and 48 arepreferably different from first and second amorphous inorganicelectrochromic counter-electrode layers 36 and 44. First and secondinorganic electrochromic layers 32 and 48 and first and second amorphousinorganic electrochromic counter-electrode layers 36 and 44 arepreferably capable of exhibiting electrochromic properties upon theincorporation of an ion such as those mentioned earlier herein. Theelectrochromic properties of first and second inorganic electrochromiclayers 32 and 48 are preferably complementary to the electrochromicproperties of first and second amorphous inorganic electrochromiccounter-electrode layers 36 and 44. Within the scope of the presentinvention, electrochromic element 28 may be interposed between twolayers of transparent substrate materials 22 and 24, such as glass orplastic.

In accordance with the invention, electrochromic element 28 can bemanufactured by sputtering a layer of a conductive electrode material ona first transparent substrate 22 or 24 to form first transparentconductive electrode 30 followed by sputtering a layer of a firstinorganic electrochromic material onto first transparent conductiveelectrode 30 to form first inorganic electrochromic layer 32. Similarly,fourth conductive electrode 50 and second inorganic electrochromic layer48 can be formed on a second glass substrate 22 or 24. A third glasssubstrate 40 can be sputtered with second transparent conductiveelectrode 38 and first amorphous inorganic electrochromiccounter-electrode layer 36 on one side and sputtered with thirdtransparent conductive electrode 42 and second amorphous inorganicelectrochromic counter-electrode layer 44 on the other side. First ionconducting layer of an electrolyte 34 can be assembled between thesputtered side of first glass substrate 22 or 24 and either side ofthird glass substrate 40. Second ion conducting layer of an electrolyte46 can then be assembled between the sputtered side of second glasssubstrate 22 or 24 and the other side of third glass substrate 40 toform electrochromic element 28.

The electrochromic element of the present invention utilizing Ni as thetransition metal in second inorganic electrochromic layer 18 and Li ionsas the insertion ions has achieved an ion exchange of 20-25 mC/cm². Theelectrochromic element of the present invention has been shown to bedurable over more than 10,000 cycles in severe conditions whileachieving complete bleaching and coloration at each cycle. Changes intransmissivity of the electrochromic element of the invention have beenachieved ranging from 30-35% to approximately 85% of visible transmittedlight when utilizing the element of FIG. 1 and also lower ranges havebeen achieved ranging from 3-5% to 55-60% of visible transmitted lightwhen utilizing the element of FIG. 2. The switching time of theelectrochromic element of the invention, i.e., the time to go from thecolored state to the bleached state is in the range of 1-10 minutes.

The following Examples are provided to illustrate the present inventionand some of its advantages. The Examples are not intended to limit theinvention.

EXAMPLE 1 Manufacture of a Solid State Device Manufacture of TransparentConductive Electrodes (TE)

Transparent conductive electrodes consisting of ITO (Indium Tin Oxide),deposited by reactive DC sputtering from an indium tin target, weredeposited on float glass (5×5 cm²) under the following conditions:

    ______________________________________                                        Initial pressure:    10.sup.-5 mb                                             Oxygen pressure:     10.sup.-3 mb                                             Argon pressure:      2.2 10.sup.-3 mb                                         Total pressure:      3.2 10.sup.-3 mb                                         Power:               400 W                                                    Voltage:             515 V                                                    Sputtering time:     10 min.                                                  Annealing:           450° C. for 30 min.                               Properties of the films:                                                      thickness = 1600 A                                                            sheet resistance R.sub.o = 50 ohms                                            optical transmission at 550 nm:                                                                    90%                                                      ______________________________________                                    

Preparation of First Inorganic Electrochromic Layer EC1

WO₃ was prepared by reactive DC sputtering from a tungsten target underthe following conditions:

    ______________________________________                                        Initial pressure:    10.sup.-5 mb                                             Oxygen pressure:     8 × 10.sup.-3 mb                                   Power:               1000 W                                                   Voltage:             490 V                                                    Sputtering time:     50 min.                                                  ______________________________________                                    

The WO₃ films thereby obtained can be either directly used orelectrochemically processed ("formated") in H₂ SO₄, 1N solution prior toutilization. A three electrode cell configuration was used for thisprocessing: the electrochromic material EC₁, a platinum counterelectrode and a saturated calomel reference electrode (SCE). Theelectrochemical treatment consisted first of a cathodic polarization ofEC₁ at 0.5 V vs. SCE for 120 seconds then followed by an anodicpolarization at +0.5 V vs. SCE for 120 seconds. This cycle was repeatedthree times and the procedure was terminated with the anodicpolarization. Finally, the films were rinsed in distilled water and thendried at room temperature.

The performance of both types of thin films (straight from sputteringand formated in H₂ SO₄) are compared in the following table(transmission measurements were carried out at 550 nm).

    __________________________________________________________________________    Thick-    Exchanged                                                                           Transm.                                                                            Transm.                                                                            Coloring                                                                           Bleaching                                      ness      charge                                                                              colored                                                                            bleached                                                                           time time                                           (A)       (mC/cm2)                                                                            (%)  (%)  (min.)                                                                             (min.)                                         __________________________________________________________________________    WO.sub.3                                                                            3000                                                                               7    45   90   6    5                                              (straight)                                                                    WO.sub.3                                                                            3000                                                                              10    35   90   4    3                                              (formated)                                                                    __________________________________________________________________________

Preparation of Second Inorganic Electrochromic Layer (EC2)

Two methods have been used:

electrochemical

physical

Electrochemical preparation involved three steps:

1st step:

The "original" layer was prepared by reactive DC sputtering from anickel target under the following conditions:

    ______________________________________                                        Initial pressure:                                                                         10.sup.-5 mb                                                                              Power:      300W                                      Oxygen pressure:                                                                          7.2 × 10.sup.-3 mb                                                                  Voltage:    240V                                      Hydrogen pressure:                                                                        0.4 × 10.sup.-3 mb                                                                  Sputtering time:                                                                          60 min.                                   Total pressure:                                                                           7.6 × 10.sup.-3 mb                                                                  Film thickness:                                                                           1100A                                     ______________________________________                                    

This produced a thin film consisting of a mixture of NiO, Ni(OH)₂ andNiOOH.

2nd step:

After sputtering, the film was electrochemically processed in NaOH, 1N,in a manner similar to that described above for WO₃, but with an anodicpolarization vs SCE for 2 min.

This yielded the formation of a layer of NiOOH and NiO. Once formated,the film was rinsed in distilled water, then dried at room temperature.

3rd step:

The final active material, namely Li_(x) Ni²⁺ _(y) Ni³⁺.sub.(2z-2y-x)/3O_(z), was obtained after an electrochemical treatment performed in adry box. The procedure utilized a two-electrode cell configuration,namely the Ni based film and a lithium electrode; both electrodes wereimmersed in LiClO₄ (1M) propylene carbonate (LiClO₄ p.c.). The film wasthen polarized at 1.7 V vs Li for 60 min. to produce the above mentionedactive material Li_(x) Ni²⁺ _(y) Ni³⁺.sub.(2z-2y-x)/3 O_(z).

Physical preparation:

Steps 1 and 2 above were replaced by reactive direct sputtering (RF)from a Li₀.3 Ni₀.7 0 target having a 75 mm diameter.

Target manufacturing:

A mixture (powder) of 0.15 Li₂ CO₃ +0.7 NiO (molar proportion) was firstheated in air at 1000° C. for 8 hours, and then compacted at 50 tons for10 mins. The material thereby obtained was finally sintered in air at1000° C. for 8 hours. The conditions for the reactive RF sputtering werethe following:

    ______________________________________                                        Initial pressure:                                                                        10.sup.-5 mb Voltage:    200V                                      Oxygen pressure:                                                                         2.5 × 10.sup.-2 mb                                                                   Sputtering time:                                                                          120mn                                     Powder:    30 W         Film thickness:                                                                           1100A                                     ______________________________________                                    

The thin film obtained by sputtering was then processed in LiClO₄ p.c.as the third step of the electrochemical method described above toproduce the final Li_(x) Ni_(1-x) O material.

The performance of both types of Ni based thin films are compared in thefollowing table (light transmission is measured at 550 nm).

    __________________________________________________________________________    Thick-    Exchanged                                                                           Transm.                                                                            Transm.                                                                            Coloring                                                                           Bleaching                                      ness      charge                                                                              colored                                                                            bleached                                                                           time time                                           (A)       (mC/cm2)                                                                            (%)  (%)  (mn.)                                                                              (mn.)                                          __________________________________________________________________________    Electro-                                                                            1100                                                                               6    45   90   30   20                                             chemical                                                                      preparation                                                                   Physical                                                                            1100                                                                              12    20   75    3    2                                             preparation                                                                   __________________________________________________________________________

Preparation of the Solid Polymer Electrolyte (SPE):

The solid polymer electrolyte was a "solid solution" of a lithium saltin a copolyether type polymer. The polymer was an ethylene oxide basedterpolymer comprising the following units: ##STR3##

An equimolar mixture of LiClO₄ and LiN(CF₃ SO₂)₂ salt was dissolved inthe polymer (15% wt.) to form the solid polymer electrolyte. Theincorporation of the salt into the polymer was operated in air by meansof a co-solvent like acetonitrile (CH₃ CN).

The above solution (polymer+salt in CH₃ CN) was spread (by adoctor-blade technique) onto the two electrodes (electrochromic films)at a thickness of 200 microns.

To remove the solvent and obtain a layer of solid polymer electrolyte oneach substrate, they were dried at 70° C. under 12 bars pressure minimum(in air). Each SPE layer obtained was 20 microns thick.

Assembly of the Complete Device

The two parts (glass+TE+EC) were then assembled together with the SPEinterposed between, in a vacuum press (0.5 mb). Prior to assembling,however, the parts were heated separately at 80° C. for 10 mins. and theair was removed out of the press chamber using a vacuum pump (0.5 mb).The parts were then pressed against each other at roughly 50 Kg/in² for3 mins.

Finally, the device was sealed (in air) with a low vapor pressure resinin order to prevent the contamination by air and moisture.

Performance of the Complete Device

A device prepared containing the electrochemically prepared Ni basedmaterial EC₂ was evaluated over a number of cycles. EC₁ was straight WO₃obtained by DC sputtering. The polymer-salt combination utilized as theion conducting layer was the terpolymer described above.

The characteristics of the device were the following:

surface area: 20 cm²

working potential range (WO₃ vs Ni based EC₂): -1.6 V for coloring; +1.4V for bleaching

charge (Li⁺) exchanged: 5-6 mC/cm²

number of cycles: over 2000

maximum transmission changes at 550 nm:

    33%→85%

times to achieve the transmission changes:

    ______________________________________                                        Transmission %:                                                                           85     35      78   40    73   45                                 Time (min.):                                                                               5     12       3    7     2    4                                 % of total trans-                                                                         100%       90%        80%                                         mission change:                                                               ______________________________________                                    

EXAMPLE 2

The preparation of this system was identical to that of Example 1 exceptthat the solid polymer electrolyte was a polyurethane network made byreacting an aliphatic triisocyanate with an α-ω hydroxylated lowmolecular weight (Mw=10,000) copolymer comprising 75% ethylene oxide and25% methyl glycidyl ether. The characteristics of this device were:

maximum transmission changes at 550 nm

    35%→83%

number of cycles: over 3,000

times to achieve the transmission changes:

    ______________________________________                                        Transmission %:                                                                              83      35       76    38                                      Time (min.):    5      12        2     4                                      % of total     100%         80%                                               transmission change:                                                          ______________________________________                                    

EXAMPLE 3

The preparation of this system was identical to that of Example 1,except that the electrolyte was a liquid electrolyte made up with asolution of LiClO₄ (1M) in propylene carbonate and EC₂ was physicallyprepared. The two electrodes (Physical Ni based EC₂ and WO₃) wereassembled against each other with a plastic spacer in between and thesystem was then filled up by the liquid electrolyte.

The characteristics of this device were:

surface area: 20 cm²

working potential range: -0.8 V for coloring, +1.9 V for bleaching

charge (Li⁺) exchanged: 5 mC/cm²

number of cycles: over 250

maximum transmission changes: 10%→58%

times to achieve the transmission changes:

    ______________________________________                                        Transmission %:                                                                              58      10       46    12                                      Time (min.):   3.5      5       2.3   1.5                                     % of total     100%         80%                                               transmission change:                                                          ______________________________________                                    

EXAMPLE 4

The preparation of this system was identical to that of Example 1,except for the nature of the electrolyte.

In this Example, the Ni based EC₂ was an "electrochemically preparedEC₂." The solid polymer electrolyte was a "solid solution" of a lithiumsalt in a copolyether type polymer. The polymer was an ethylene oxidebased terpolymer comprised of: ##STR4##

The lithium salt was Li N(CF₃ SO₂)₂, incorporated in the polymer at 20%(wt.).

The characteristics of the devices were:

surface area: 20 cm²

working potential range: -1.6 V for coloring, +1.4 V for bleaching

charge (Li⁺) exchanged: 5 mC/cm²

number of cycles: over 300

maximum transmission changes: 40%→80%

times to achieve the transmission changes:

    ______________________________________                                        Transmission %:                                                                              80      40       65    33                                      Time (min.):    5      10        2     4                                      % of total     100%         80%                                               transmission change:                                                          ______________________________________                                    

EXAMPLE 5

The preparation of this system was identical to that of Example 1 exceptfor the transparent conductive electrodes, the Ni based EC₂ and thesolid polymer electrolyte. In this Example, the Ni based EC₂ was an"electrochemically prepared EC₂." The transparent conductive electrodeswere SnO₂ : F (fluorine doped tin oxide) prepared by chemical vapordeposition. The solid polymer electrolyte was a "solid solution" of alithium salt in a copolyether type polymer. The polymer was an ethyleneoxide based copolymer comprised of: ##STR5##

An equimolar mixture of LiClO₄ and LiN(CF₃ SO₂) ₂ salt was dissolved inthe polymer (15% wt.) to form the solid polymer electrolyte.

The characteristics of the device were:

surface area: 20 cm²

working potential range: -1.6 V for coloring +1.4 V for bleaching

charge (Li⁺) exchanged: 5-6 mC/cm²

number of cycles: over 300

maximum transmission changes: 37%→83%

times to achieve the transmission changes:

    ______________________________________                                        Transmission %:                                                                              83      37       78    41                                      Time (min.):    5      11        2     4                                      % of total     100%         80%                                               transmission change:                                                          ______________________________________                                    

EXAMPLE 6

A Ni based thin film EC2 was prepared by R.F. sputtering with thefollowing parameters:

power: 120 W

initial pressure: 10⁻⁷ mb

oxygen pressure: 8×10⁻² mb

total pressure: 8×10⁻² mb

sputtering time: 30 min.

substrate: float glass coated with SnO₂ :F 2.5×2.5 cm²

thickness: (at the edge of the substrate): 800 angstroms

A film of solid polymer electrolyte (S.P.E.) was then deposited byin-situ crosslinkage, forming: glass/TE/EC2/SPE. A lithium foil was thenapplied to form the electrochemical cell:

    glass/TE/EC2/SPE/Li/Copper.

This electrochemical cell was then cycled 50 times at voltages:

    ______________________________________                                        +1.5 volt for 500 seconds (insertion of Li.sup.+  in EC2)                     +3.5 volt for 300 seconds (extraction of Li.sup.+  from                       ______________________________________                                        EC2)                                                                      

The charge exchanged is reported in the following table and compared toan identical sample cycled in a liquid electrolyte:

    ______________________________________                                        Q (mC/cm.sup.2)  cycle n°2                                                                       cycle n°50                                   ______________________________________                                        Solid electrolyte                                                                              26.0     22.0                                                Liquid electrolyte                                                                             24.8     12.4                                                ______________________________________                                    

After the 50 cycles, the copper/Li/SPE was removed by peeling and theglass/TE/EC2 was assembled in a final device with a WO₃ =EC1 electrode.This device was cycled according to the voltages:

    ______________________________________                                        ΔV = V.sub.EC 1 - V.sub.EC2 = -0.6V for 85 seconds (coloration)         ΔV = +1.6 volts for 45 seconds (decoloration)                           ______________________________________                                    

and then exchanged 10.0 mC/cm² with a transmission change at λ=550 nm of55% to 10%.

EXAMPLE 7

A chromium based EC2 film with the formula

    M.sub.x T.sup.n.sub.y T.sup.n+m.sub.(uz-ny-x)/(n+m) X.sub.z.sup.u

where:

M=Li

T=Cr

n=3

m=1 Li_(x) Cr^(III) _(y) Cr^(IV).sub.(4-3y-x)/4 O₂

X=O

u=2

z=2

was prepared by R.F. sputtering of a target LiCr0₂ with the followingparameters:

Power: 100 W

Initial pressure: 10⁻⁷ mb

Argon pressure: 6×10⁻³ mb

Total pressure: 6×10⁻³ mb

Sputtering Time: 35 minutes

Thickness: 1250 Å

Substrate: float glass coated with indium tin oxide.

The film was then electrochemically processed in LiClO₄ (1M) inpropylene carbonate solvent. It was cycled 10 times at voltages:

1.2 volts vs Lithium for 300 seconds (insertion of Li⁺)

3.5 volts for 600 seconds (extraction of Li⁺)

with a corresponding transmission change from 71% to 91%. The exchangedcharge was in the vicinity of 50 mC/cm². After drying and cleaning ofthe film, it was assembled in a complete device identical to Example 2(polyurethane network) with a WO₃ EC1 electrode.

The device was cycled according to

ΔV=V_(EC1) -V_(EC2) =-0.8 V for coloring for 380 seconds

ΔV=+1.4 volts for bleaching (at 30° C.)

with a charge exchanged of approximately 10 mC/cm² and a transmissionchange from 33% to 79% (at 550 nm). The number of cycles was over 4,000.

The electrochromic element of the present invention can be useful inapplications such as for sun roofs of automobiles, architecturalwindows, aircraft windows, the rear windows of vans or trucks, or insunglasses. The electrochromic element of the invention can be utilizedto vary the amount of visible light transmitted through a substrate andalso can be utilized to reduce the amount of radiant heat transmittedthrough windows. Alternatively, the electrochromic element of theinvention can be utilized in a mirror to vary the percentage ofreflected visible light which would be useful, for example, in anautomobile rear view mirror.

It has also been found that the electrochromic element of the inventioncan be useful as a supercapacitor. Of course, the electrochromicproperties of the element of the invention are not necessary in asupercapacitor. However, it has been found that a laminate consisting ofan ion conducting layer of an electrolyte interposed between first andsecond inorganic electrochromic layers, all sandwiched between a pair ofconductive substrates such as plastic sheets, having a thickness on theorder of 200 microns, provides an element which is useful as asupercapacitor, having favorable values of specific capacitance,specific energy, leakage current and thermal stability. Such a laminateutilizing an ion conducting layer of an electrolyte and first and secondinorganic electrochromic layers in accordance with the invention iscapable of providing a specific capacitance on the order of 1 Farad/cm³.

Although the present invention has been described in connection with thepreferred embodiments, it is understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention. Such modifications are considered to be withinthe purview and scope of the invention and the appended claims.

What is claimed is:
 1. An electrochromic element comprising a pair ofconductive electrodes at least one of which is transparent, first andsecond inorganic electrochromic layers interposed between said pair ofconductive electrodes and an ion conducting layer of an electrolyteinterposed between said first and second inorganic electrochromiclayers, wherein said first and second inorganic electrochromic layersare different and are capable of exhibiting electrochromic propertiesupon the incorporation of at least one ion of an element selected fromthe group consisting of H, Li, Na, K, Ag, Cu and Tl, wherein said secondinorganic electrochromic layer is amorphous, wherein the electrochromicproperties of said first and second inorganic electrochromic layers arecomplementary, and wherein said second inorganic electrochromic layercomprises the composition

    M.sub.x T.sup.n.sub.y T.sup.n+m.sub.(uz-ny-x)/(n+m) X.sup.u.sub.z,

wherein x, y, z, u≧0, 2≦n≦3, 1≦m≧2, n+m≦4; T is a fourth periodtransition element selected from Ni, Co, Mn, Cr, V, Ti or Fe; M is atleast one element selected from H, Li, Na, K, Ag, Cu and Tl; X isselected from O, S, F and Cl; n, n+m and u are oxidation numbers; and xis the moles of M⁺ ions incorporated into said second inorganicelectrochromic layer, y is the moles of T at the oxidation number n andz is the moles of X.
 2. The element of claim 1, wherein said ionconducting layer of an electrolyte is an amorphous solution of anionizable salt in a polymer capable of conducting an amount of an ionselected from H, Li, Na, K, Ag, Cu and Tl ions between said first andsecond inorganic electrochromic layers sufficient to cause each of saidfirst and second inorganic electrochromic layers to exhibit acomplementary color change, with said ion conducting layer remainingamorphous and transparent.
 3. The element of claim 2, wherein said firstinorganic electrochromic layer is WO₃.
 4. The element of claim 2,wherein said first inorganic electrochromic layer is MoO₃.
 5. Theelement of claim 2, wherein said first inorganic electrochromic layer isTiO₂.
 6. The element of claim 1, 2, or 3, wherein said pair ofconductive electrodes are fluorine doped tin oxide (SnO₂ :F).
 7. Theelement of claim 1, 2, and 3, wherein said pair of conductive electrodesare indium-tin oxide.
 8. The element of claim 1 or 2, wherein said ionconducting layer of an electrolyte comprises a copolymer of ethyleneoxide and at least one comonomer selected from methyl glycidyl ether,propylene oxide, butylene oxide and allyl glycidyl ether, and at leastone ionizable salt.
 9. The element of claim 1 or 2, wherein said ionconducting layer of an electrolyte comprises:a polyurethane gel formedby reacting a triisocyanate with an α-ω hydroxylated copolymer ofethylene oxide and at least one comonomer selected from methyl glycidylether, propylene oxide, butylene oxide and allyl glycidyl ether, saidcopolymer having a molecular weight ranging between 1,000 and 20,000;and at least one ionizable salt.
 10. The element of claim 1, whereinsaid second inorganic electrochromic layer is formed by sputtering atarget of transition metal T with an O₂ /H₂ plasma to form an originallayer consisting essentially of a mixture of TO, T(OH)₂ and TOOH;electrochemically processing the original layer in alkali metalhydroxide solution to form a layer consisting essentially of TO andTOOH; and electrochemically processing the formatted layer consistingessentially of TO and TOOH in a liquid electrolyte comprising a polarsolvent and an ionizable salt of a strong acid and an element selectedfrom H, Li, Na, K, Ag, Cu and Tl, to form said second inorganicelectrochromic layer having the composition

    M.sub.x T.sup.n.sub.y T.sup.n+m.sub.(2z-ny-x)/(n+m) O.sub.z.


11. The element of claim 1, wherein said second inorganic electrochromiclayer is formed by sputtering a target of MαT₁₋α O, wherein 0<α≦1.0, toform a thin film which comprises M,T^(n),T^(n+m) and O,electrochemically processing the thin film in a liquid electrolytecomprising a polar solvent and an ionizable salt of a strong acid and anelement selected from H, Li, Na, K, Ag, Cu and Tl, to form said secondinorganic electrochromic layer having the composition

    M.sub.x T.sup.n.sub.y T.sup.n+m.sub.(2z-ny-x)/(n+m) O.sub.z.


12. The element of claim 1, wherein M⁺ ions are capable of beinginserted from said ion conducting layer to said first inorganicelectrochromic layer to form the composition M_(t) WO₃, which iscolored, wherein 0≦t≦1 and t is moles of M.
 13. The element of claim 12,capable of exhibitinga) a first color state wherein said secondinorganic layer is bleached and has the composition M_(x) T_(y) ^(n)X_(z) ^(u) and said first inorganic layer is bleached and has thecomposition

    WO.sub.3, and

b) a second color state wherein said second inorganic layer is coloredand has the composition M_(x-)Δx T^(n) _(y-)Δx/m T^(n+m).sub.Δx/m X^(u)_(z) and said first inorganic layer is colored and has the composition

    M.sub.Δx WO.sub.3,

said first color state having a maximum transmissivity and said secondcolor state having a less than maximum transmissivity.
 14. The elementof claim 1, wherein X is O.
 15. The element of claim 14, wherein M isLi.
 16. The element of claim 1, wherein said M⁺ ions can be insertedinto said second inorganic electrochromic layer by applying a voltagedifferential between said pair of conductive electrodes.
 17. The elementof claim 12, wherein said M⁺ ions can be inserted into said firstinorganic electrochromic layer by applying a voltage differentialbetween said pair of conductive electrodes.
 18. An electrochromic devicecomprising the element of claim 7 interposed between a pair oftransparent substrates.
 19. The electrochromic device of claim 18,wherein said pair of transparent substrates are glass.
 20. Theelectrochromic device of claim 18, wherein said pair of transparentsubstrates are plastic.
 21. An electrochromic element comprising thefollowing layers, in order: a first transparent conductive electrode; afirst inorganic electrochromic layer; a first ion conducting layer of anelectrolyte; a first amorphous inorganic electrochromic counterelectrode layer; a second transparent conductive electrode, atransparent substrate; a third transparent conductive electrode; asecond amorphous inorganic electrochromic counter-electrode layer; asecond ion conducting layer of an electrolyte; a second inorganicelectrochromic layer and a fourth conductive electrode which may betransparent or reflective; wherein said first and second inorganicelectrochromic layers are different from said first and second amorphousinorganic electrochromic counter electrode layers; said first and secondinorganic electrochromic layers and said first and second amorphousinorganic electrochromic counter electrode layers are capable ofexhibiting electrochromic properties upon the incorporation of ions ofat least one element selected from H, Li, Na, K, Ag, Cu and Tl; and theelectrochromic properties of said first and second inorganicelectrochromic layers are complementary to the electrochromic propertiesof said first and second amorphous inorganic electrochromic counterelectrode layers, and wherein at least one of said first and secondinorganic electrochromic layers comprises the composition

    M.sub.x T.sup.n.sub.y T.sup.n+m.sub.(uz-ny-x)/(n+m) X.sup.u.sub.z,

wherein x, y, z, u≧0, 2≦n≦3, 1≦m≦2, n+m≦4; T is a fourth periodtransition element selected from Ni, Co, Mn, Cr, V, Ti or Fe; M is atleast one element selected from H, Li, Na, K, Ag, Cu and Tl; X isselected from O, S, F and Cl; n, n+m and u are oxidation numbers; and xis the moles of M⁺ ions incorporated into said first and secondinorganic electrochromic layers, y is the moles of T at the oxidationnumber n and z is the moles of X.
 22. An electrochromic devicecomprising the element of claim 21 interposed between a pair oftransparent substrates.
 23. An amorphous electrochromic material havingthe formula: M_(x) T^(n) _(y) T^(n+m).sub.(uz-ny-x)/(n+m) X^(u) _(z),wherein x, y, z, u≧0, 2≦n≦3, 1≦m≦2, n+m≦4; M is at least one elementselected from H, Li, Na, K, Ag, Cu and Tl; X is selected from O, S, Fand Cl; T is selected from Ni, Co, Mn, Cr, V, Ti and Fe; n, n+m and uare oxidation numbers; and x is the moles of M⁺ ions incorporated intothe amorphous electrochromic material, y is the moles of T at theoxidation number n and z is the moles of X.
 24. The amorphouselectrochromic material of claim 23, wherein M is Li.
 25. The amorphouselectrochromic material of claim 23 or 24, wherein X is O.
 26. A processfor producing an amorphous electrochromic material comprising:a firststep of forming an original thin film consisting essentially of amixture of TO, T(OH)₂ and TOOH by sputtering a target comprising T withan O₂ /H₂ plasma; a second step of electrochemically processing theoriginal thin film in alkali metal hydroxide solution to give a layerconsisting essentially of TO and TOOH; a third step of electrochemicallyprocessing the layer consisting essentially of TO and TOOH in a liquidelectrolyte comprising a polar solvent and an ionizable salt of a strongacid and an element selected from H, Li, Na, K, Ag, Cu and Tl, toincorporate xM⁺ ions into the layer consisting essentially of TO andTOOH to form an amorphous electrochromic material having the compositionM_(x) T^(n) _(y) T^(n+m).sub.(2z-ny-x)/(n+m) O_(z) ; wherein T is atransition element of the fourth period of the periodic table having anoxidation number ranging from 2 to 4 and is selected from Ni, Co, Mn,Cr, V, Ti and Fe; n and n+m represent oxidation numbers; and x, y and zrepresent moles.
 27. A process for producing an amorphous electrochromicmaterial comprising:a first step of sputtering a target of M.sub.α T₁₋αO, wherein 0<α≦1.0, to form a thin film which comprises M, T^(n),T^(n+m)and O; a second step of electrochemically processing the thin film in aliquid electrolyte comprising a polar solvent and an ionizable salt of astrong acid and an element selected from H, Li, Na, K, Ag, Cu and Tl, toincorporate M⁺ ions in the thin film to form an amorphous electrochromicmaterial having the composition M_(x) T^(n) _(y)T^(n+m).sub.(2z-ny-x)/(n+m) O_(z) ; wherein T is a transition element ofperiod four of the periodic table selected from Ni, Co, Mn, Cr, V, Tiand Fe; n and n+m represent oxidation numbers and x, y and z representmoles.
 28. A process of forming the amorphous electrochromic material ofclaim 24 comprising:sputtering a layer of a conductive electrodematerial on a first substrate; sputtering a layer on an amorphousinorganic electrochromic material onto said conductive electrode layeron said first substrate; depositing a solid polymer electrolyte ontosaid amorphous inorganic electrochromic layer; assembling a lithiumelectrode on a second substrate into juxtaposed contact with said solidpolymer electrolyte; applying a first voltage differential between saidconductive electrode material and said lithium electrode to incorporatelithium ions into said amorphous inorganic electrochromic layer;applying a second voltage differential between said conductive electrodematerial and said lithium electrode to remove lithium ions from saidamorphous inorganic electrochromic layer; and removing said lithiumelectrode on said second substrate and said solid polymer electrolytefrom said amorphous inorganic electrochromic layer.
 29. A process ofmanufacturing the device of claim 18, comprising:sputtering a layer of aconductive electrode material on a first substrate; sputtering a layerof an inorganic electrochromic material onto said conductive electrodelayer on said first substrate; sputtering a layer of a conductiveelectrode material on a second substrate; sputtering a layer of anamorphous inorganic electrochromic material onto said conductiveelectrode layer on said second substrate; and assembling an ionconducting layer of a solid polymeric electrolyte between the sputteredsides of said first and second substrates.
 30. The process of claim 29,further comprising electrochemically processing at least one of saidamorphous inorganic electrochromic material and said inorganicelectrochromic material prior to assembling said ion conducting layerbetween said first and second substrates.
 31. A process of manufacturingthe device of claim 22, comprising:sputtering a first layer of aconductive electrode material on a first substrate; sputtering a firstlayer of an inorganic electrochromic material onto said first conductiveelectrode layer on said first substrate; sputtering a second layer of aconductive electrode material on a second substrate; sputtering a secondlayer of an inorganic electrochromic material onto said secondconductive electrode layer on said second substrate; sputtering a thirdlayer of a conductive electrode material on one side of a thirdsubstrate and a fourth layer of a conductive electrode material on theother side of said third substrate; sputtering a layer of an amorphousinorganic electrochromic material on said third and fourth conductiveelectrode layers on each side of said third substrate; assembling thesputtered side of said first substrate into juxtaposed contact with oneside of said third substrate with an ion conducting layer of a polymericelectrolyte interposed therebetween; and assembling the sputtered sideof said second substrate into juxtaposed contact with the other side ofsaid third substrate with an ion conducting layer of a polymericelectrolyte interposed therebetween.
 32. The process of claim 31,further comprising electrochemically processing at least one of saidamorphous inorganic electrochromic material and said inorganicelectrochromic material prior to said assembling steps.
 33. Anelectrochromic mirror device comprising the electrochromic element ofclaim 1, 2, or 3, interposed between a pair of substrates, wherein oneof the conductive electrodes is reflective and the other is transparent.34. An electrochromic device comprising a plurality of electrochromicelements as recited by claims 1, 2, or 3, in juxtaposed surface tosurface relation, wherein a transparent substrate is interposed betweeneach pair of electrochromic elements and the plurality of electrochromicelements are interposed between a pair of transparent substrates.